Understanding Derechos: The Powerful Storms that Bring Heavy Rainfall and Strong Winds
Prolonged wind events that unleash heavy rainfall and travel far distances sometimes qualify as derechos. These powerful storms can bring significant damage and disruption to daily life, making it essential to understand what they are and how to prepare for them.
Derechos can happen almost anywhere in the United States, but are most common in the central and eastern regions of the country. Winds typically gust over 60 miles per hour and can cause damage comparable to tornadoes or hurricanes. Here’s what you need to know about this extreme weather event.
What is a Derecho?
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A derecho is a long-lived line of storms that often produces extreme wind damage, said Gino Izzi, a meteorologist at the National Weather Service’s office in Chicago. Derechos, which must be more than 240 miles long, can last eight hours or longer and travel hundreds of miles across the country.
“There’s been instances where derechos have moved from Iowa all the way to Washington, D.C.,” Izzi said. Because of the intense straight-line winds and vast distances a derecho can travel, the damage they cause is sometimes comparable to the destructive forces of tornadoes or hurricanes.
Hurricanes are low-pressure systems that form over tropical or subtropical ocean waters and have organized thunderstorm activity, according to the National Oceanic and Atmospheric Administration. Unstable air that is hot and humid is supportive of derecho formation, forecasters say. Derechos can happen any time of year, but July and early August are the prime time for this type of extreme weather, Izzi said.
Types of Derechos
Derechos are an uncommon weather event and usually a small number occur each year, but Izzi said several years could pass without a recorded derecho. There are different types of derechos. Serial derechos tend to form with large, powerful storms and typically occur in early spring, fall and early winter.
Progressive derechos are usually smaller and tend to form in summer as they feed off of hot, humid conditions. Hybrid derechos have characteristics of both serial and progressive types. Conditions that are favorable for derechos can also lead to small, embedded tornadoes, which are violently rotating columns of air that extend down from a thunderstorm and reach the ground.
Safety Tips
Derechos tend to produce much more widespread damage than tornadoes because they can produce a swath of damage that exceeds 100 miles in width, whereas the damage from violent tornadoes is typically less than a mile wide. Safety tips include using a radio to listen to the forecast, monitoring devices for severe weather alerts from the NWS and having access to a sturdy shelter.
“It can go from nice, calm weather to 100 miles per hour winds blowing down trees in literally a matter of minutes,” said Izzi. It is crucial to stay informed and be prepared for the unexpected when it comes to derechos.
Where do Derechos Form?
Derechos can happen almost anywhere in the U.S. but are most common in the central and eastern regions of the United States. Progressive derechos tend to favor the northern and central Plains eastward into the Midwest, Great Lakes, and Ohio Valley area.
That is because domes of heat can form across central parts of the U.S. and derechos tend to form on the northern and northeastern flanks of the dome, where there are high levels of atmospheric instability. This also tends to be where the jet stream winds are stronger. Humidity from crops like corn, also known as corn sweat, magnifies how unstable the hot, humid air is.
Notable Derecho Events
Derechos are not as common in Texas, according to the National Weather Service’s Fort Worth office, but one in Houston did cause notable damage in 2024. A 2009 storm dubbed a Super Derecho by meteorologists traveled from western Kansas to eastern Kentucky.
It caused several deaths and injuries and more than $500 million in damages by the time it had traveled more than 1,000 miles. In December 2021, a derecho in the Great Plains and Upper Midwest spawned at least 45 tornadoes, caused widespread damage and killed at least five people.
Derechos can Cause Flash Flooding
Derechos can be associated with a slow-moving or nearly stationary band of thunderstorms. This could potentially lead to heavy rainfall and flash floods that can cause significant damage. Flash floods associated with a derecho that occurred July 4-5, 1969, caused Killbuck Creek in Ohio to rise more than 20 feet above normal level and at least two dozen fatalities, according to NOAA.
Conclusion
In conclusion, derechos are powerful storms that can bring heavy rainfall, strong winds, and significant damage. Understanding what derechos are, how they form, and where they are most common can help individuals prepare and stay safe during these events. By staying informed and following safety tips, we can minimize the impact of derechos and protect ourselves and our communities.
Frequently Asked Questions
Q: What is a derecho?
A: A derecho is a long-lived line of storms that often produces extreme wind damage, characterized by a large, continuous area of thunderstorms that can last for several hours or even days.
Q: Where do derechos most commonly occur?
A: Derechos can happen almost anywhere in the United States, but are most common in the central and eastern regions of the country.
Q: What type of damage can derechos cause?
A: Derechos can cause significant damage, including downed trees, power outages, and structural damage to buildings and homes.
Q: Can derechos cause flash flooding?
A: Yes, derechos can be associated with slow-moving or nearly stationary bands of thunderstorms, which can lead to heavy rainfall and flash flooding.
Q: How can I stay safe during a derecho?
A: To stay safe during a derecho, it is essential to stay informed, monitor weather forecasts and alerts, and have access to a sturdy shelter. Additionally, using a radio to listen to the forecast and having a plan in place can help minimize the risk of injury or damage.
